Transformer-inductor frame and kit

ABSTRACT

A transformer or inductor frame for holding together two E cores and a coil. The transformer frame includes two leaf springs integral with the back of the frame and having bendable tabs integral with the forward portion of the legs of the frame. The tabs and spring act together to hold the two E cores together and to maintain the core and coil assembly in the frame. The frame together with an E core having slightly increased leg cross section dimensions and a bobbin constitutes a kit for the winding of a transformer or inductor.

United States Patent Horbach TRANSFORNIER-INDUCTOR FRAME AND KIT [72] Inventor: Stephen Horbach, Mountain Lakes, NJ. [73] Assignee: Electronic Associates, Inc., West Long 7 Branch, NJ. [22] Filed: Mar. 8, 1971 [21] App1.No.: 121,826

[52] US. Cl ..336/2l0 [51] Int. Cl. ..Il0lf 27/26 [58] Field ofSearch ..336/65,210,212, 198

[56] References Cited UNITED STATES PATENTS 2,903,661 9/1959 Goffstein ..336/65 2,431,867 12/1947 Galla 336/210 X 3,584,823 6/1971 Andrew et al ..336/65 X 3,011,140 11/1961 Mittermaier et al. ..336/l98 [451 June 6,1972

1,974,588 9/1934 2,898,564 8/1959 Terry,.lr. ..336/210X FOREIGN PATENTS OR APPLICATIONS 1,247,742 10/1960 France ..336/65 388,803 1933 GreatBritain ..336/2l0 Primary Examiner-Thomas J. Kozma Attorney-Ryder, McAulay & l-lefter [57] ABSTRACT A transformer or inductor frame for holding together two E cores and a coil. The transformer frame includes two leaf springs integral with the back of the frame and having bendable tabs integral with the forward portion of the legs of the frame. The tabs and spring act together to hold the two E cores together and to maintain the core and coil assembly in the frame. The frame together with an E core having slightly increased leg cross section dimensions and a bobbin constitutes a kit for the winding of a transformer or inductor.

8 Claim, 4 Drawing Figures Snell ..336/210 TRANSFORMER-INDUCTOR FRAME AND KIT This invention relates in general toa transformer or inductor assembly which is particularly adapted to be provided as a kit of separate E core units, a bobbin unit, and a frame unit which, after the oil is wound on the core, can'readily be fabricated into'the desired transformer'or inductor.

BACKGROUND or THE INVENTION One type of the many known transfonner assemblies involves the use of two matching E cores. There are a number of techniques for holding the cores together around the bobbin. These techniques include the use of tape and the use of a metal bracket having two or more parts with or without integral springs. .All such techniques require an appreciable amount of hand labor.

Accordingly, it is a major purpose of this invention to provide a transformer assembly design in which the amount of hand labor and time required to assemble the transformer is substantially reduced.

It is another purpose of this invention to provide a simple transformer assembly design which can be assembled without requiring the use of tools.

It is a further related purpose of this invention to meet the above purposes with a minimum number of parts.

Thus, low cost and simplicity are major objects of this invention because it is in low cost and in simplicity that there is provided an improvement over previously known designs.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and purposes of this invention will become apparent from the following detailed description and drawings, in which:'

FIG 1 is an exploded perspective view of a transformer assembly embodiment of this invention;

FIG. 2 is a perspective view of the FIG. 1 device assembled;

FIG. 3 is a longitudinal sectional view through the frame unit shown in FIG. I showing the leaf spring arrangement at the back of the frame; and

F IG. 4 is an end view of the back'of the FIG. 3 frame;

BRIEF DESCRIPTION or THE INVENTION In brief, this invention employs two matching ferrite E shaped cores and a bobbin which fits over the center leg of the E cores. The end legs of the E cores fit within opposed channelsof a unitary stainless steel frame structure. The frame structure is a three sided element, each side being in the form of a channel. The two legs of the channel fit over the end legs of the E cores. The back end of the channel has a leaf spring extending inward to contact a back end surface of one of the two E cores. There are bendable tabs at the front ends of each of the two channel legs. When the E cores and coil carrying bobbin assembly is inserted into the channel, it is pressed back against the leaf spring and the tabs are bent in to hold the E cores and coil carrying bobbin in place. The frame includes prongs and feet for holding the assembled transformer onto a circuit board or chassis.

The two end legs of the E core are approximately 6 percent greater in cross sectional area than required for the flux capacity. Thus chipping of the core results in minimal loss of required magnetic properties.

The frame together with E cores and bobbin constitutes a kit that can be used to fabricate the transformer or inductor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the figures, which all represent one embodiment of this invention, there is a transformer coil 10 having windings l2 wound on a bobbin 14, the bobbin leads l6 permit making appropriate electrical connections to the windings l2.

Two, essentially identical E shaped core units 18, 20 are fitted around the coil 10. These E core units 18, 20 are made of a ferrite material having the required permeability.

A unitary stainless steel frame structure 22 holds the E core 18, 20 and coil 10 unit together and further provides a means for mounting the assembled transformer onto a chassis. Broadly, this frame 22 can be considered to have three sides, specifically two legs 23 and a back 24. Each of these sides 23, 24 is in the form of a channel. The E cores 18, 20 slide into the channel with a slip-fit engagement.

The frame 22 includes four tabs 25 and a two leaf springs 26. The tabs 25 and leaf springs 26 cooperate to hold the E core and coil assembly rigidly together within the channel formed by the frame 22.

In addition, the frame 22 has a dual mount structure comprising two prongs 28 and two feet 30. Each foot 30 has a central opening through which a screw, eyelet or rivet can be accepted.

As shown in FIG. 1, the four tabs 25 are formed on the sides of the leg 23 channels by appropriate cuts in the sides of these channels. By comparing FIG. 2 with FIG. 1, it can be seen that in assembly, after the E cores 18, 20 and coil 10 are inserted into the channels and pressed back against the leaf springs 26, the tabs 25 are bent into the channel area to hold the E cores in the channel against spring pressure.

The frame 22 is a unitary item bent and punched out of a single sheet of corrosion resistant non-magnetic material that can function as a spring. A stainless Grade 301, one-fourth hard, having a thickness 0.015 inches has been found to operate satisfactorily.

When assembled, the two leaf springs 26 are forced back approximately one-half distance from their unstrained position. For example, in one embodiment the two leaf springs 26 are formed out of the back surface 32of the frame 22 so that the springs 26 extends into the channel mils (0.12 inch). This is, the dimension 0 in FIG. 3 is 120 mils. When assembled, the nominal dimensions of the E core 18, 20 and frame 22 are such that the springs are pushed back to a distance 60 mils into the channel. This gives sufficient leeway so that manufacturing tolerances in the E cores 18, 20 and in the frame 22 can be accommodated by retaining spring pressure on the E cores to force them against the bent-in tabs 25.

The two springs 26 are lanced out of the surface 32, formed and then work hardened to provide spring qualities. The springs are formed so that they contact the E core 18 with a contact surface 265 that is flat and parallel to the back surface of the E core 18. Thus, the springs 26 do not dig into the E core 18 and are able to ride with the E core and perform their spring function unhindered and without damage to the E core.

Use of two springs 26 has the advantage that a skewed spring force is minimized. More importantly, if one of the springs 26 breaks or is two weak a spring, the other spring remains effective to perform the desired function.

The prongs 28 represent the sheet steel material left when forming the openings of the feet 30. The top edge of the prongs 28 are scored, as at the line 34, so that if desired, the prongs can be bent back and forth a few times and cause to break off. However, in many applications the prongs 28 are useful to hold the assembled transformer on a board. The prongs can be inserted through openings in the circuit board and then bent under or twisted to hold the transformer to the board. The feet 30 have openings which pemIit the use of a fastener to hold the frame 22 and thus the entire transformer assembly onto a chassis. Prongs 28 or feet 30 or both may be employed. I

One important feature of the two matching E cores 18, 20 is that, in this preferred embodiment, the cross sectional area of the E core end legs 18a, 20a, is made to be 6 percent greater than would be required for the given cross sectional area of the center leg 18c, 20c. Fenite cores, as contrasted with the laminated cores, tend to chip in handling, particularly at the edges of the end legs 18a, 20a. The small amount of chipping reduces the flux path and impares magnetic properties. By

building in a 3 percent increase along each side of each end leg, a small amount of chipping can be tolerated without reducing the flux through the transformer. This improves transformer performanceand extends the effective life of the transfonner.

One of the main advantages of the above described design is that the bobbin 14, without the winding 12, together with the two E cores l8, and the-matching frame 22 can be provided as a kit which can then readily be employed by the equipment manufacturer who winds the winding 20 on the bobbin 14 and then assembles, in a simple fashion, the parts shown in FIG. 1

into the assembled transformer shown in FIG. 2.

What is claimed is:

1. A unitary stainless steel frame for holding together the assembly of a coil and a multiple-piece ferrite core comprising:

a channel having a first leg portion, a second leg portion, and a back portion connecting said legs and integral with said legs, each of said portions of said channel having two side surfaces connected by a back surface,

a first leaf spring integral with and formed out of said back surface of said back portion of said channel, said leaf spring extending into said channel at said back portion,

a plurality of bendable tabs integral with said leg portions of said channel and positioned at the opening of said leg portions,

said tabs having a first position in-which said openings of said leg portions of said channel are unobstructed so that the core can be inserted into said leg portions,

each of said tabs when in said first position extending forward from said back surface of the leg portion of said channelwith which the tab is associated with being substantially co-planar with one of said surfaces of the leg portion with which the tab is associated, each of said tabs being bendable about an axis substantially parallel to said back surface of the leg portion with which the tab is associated,

said tabs having a second position in which said tabs obstruct said openings of said leg portions of said channel,

the edges of said tabs when in said second position serving to contact whatever assembly of core and coil is in said 1 channel to prevent the assembly from being moved out of the channel and to hold the assembly back against said leaf spring,

v whereby a unitary frame is provided for firmly holding the portions of the core together.

2. The frameof claim 1 further comprising:

a second leaf spring integral with and formed out of said back surface of said back portion of said channel, and extending into said channel at said back portion.

3. The frame of claim 1 wherein:

said first leaf spring has a flat portion for contacting a back surface of the core, said flat portion of said leaf spring being substantially parallel to the back surface of the core when the core is inserted into said channel.

4. The frame of claim 2 wherein:

said first and second leaf springs each have a flat portion for contacting a back surface of the core, said flat portions of said leaf springs being substantially parallel to the back surface of the core when the core is inserted into said channel.

5. The frame improvement of claim 1 wherein:

said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.

6. The frame improvement of claim 2 wherein:

said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.

7. The frame im rovement of claim 3 wherein: said plurality 0 tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.

8. The frame improvement of claim 4 wherein:

said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of saidfirst leg portion, a third tab and fourth tab being spaced from one another across the channel entrance of said second leg portion. 

1. A unitary stainless steel frame for holding together the assembly of a coil and a multiple-piece ferrite core comprising: a channel having a first leg portion, a second leg portion, and a back portion connecting said legs and integral with said legs, each of said portions of said channel having two side surfaces connected by a back surface, a first leaf spring integral with and formed out of said back surface of said back portion of said channel, said leaf spring extending into said channel at said back portion, a plurality of bendable tabs integral with said leg portions of said channel and positioned at the opening of said leg portions, said tabs having a first position in which said openings of said leg portions of said channel are unobstructed so that the core can be inserted into said leg portions, each of said tabs when in said first position extending forward from said back surface of the leg portion of said channel with which the tab is associated with being substantially co-planar with one of said surfaces of the leg portion with which the tab is associated, each of said tabs being bendable about an axis substantially parallel to said back surface of the leg portion with which the tab is associated, said tabs having a second position in which said tabs obstruct said openings of said leg portions of said channel, the edges of said tabs when in said second position serving to contact whatever assembly of core and coil is in said channel to prevent the assembly from being moved out of the channel and to hold the assembly back against said leaf spring, whereby a unitary frame is provided for firmly holding the portions of the core together.
 2. The frame of claim 1 further comprising: a second leaf spring integral with and formed out of said back surface of said back portion of said channel, and extending into said channel at said back portion.
 3. The frame of claim 1 wherein: said first leaf spring has a flat portion for contacting a back surface of the core, said flat portion of said leaf spring being substantially parallel to the back surface of the core when the core is inserted iNto said channel.
 4. The frame of claim 2 wherein: said first and second leaf springs each have a flat portion for contacting a back surface of the core, said flat portions of said leaf springs being substantially parallel to the back surface of the core when the core is inserted into said channel.
 5. The frame improvement of claim 1 wherein: said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.
 6. The frame improvement of claim 2 wherein: said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.
 7. The frame improvement of claim 3 wherein: said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and a fourth tab being spaced from one another across the channel entrance of said second leg portion.
 8. The frame improvement of claim 4 wherein: said plurality of tabs are four in number, a first tab and a second tab being spaced from one another across the channel entrance of said first leg portion, a third tab and fourth tab being spaced from one another across the channel entrance of said second leg portion. 